CN201065573Y disclosed a dual water-sealed and negative pressure toilet, wherein, an upper trap 3, which is positioned in a bucket body 1 and is connected with the lower port of a urinal 2, is connected with a lower trap 5 via a down drain tube 4, the lower trap 5 is connected downwards with a down drain outlet 6 via the drain tube 4; the upper trap 3 is connected with the lower trap 5 via the down drain tube 4. The utility model is characterized in that a down water seal is added on the basis of one water seal in the siphon toilet to form dual water seal and dual siphon, thus has the advantages of smell isolation, water saving, splash prevention, noise prevention; But the dual water-sealed and negative pressure toilet has the following problems: because there is air existing in the drain tube 4 between the upper trap 3 and lower trap 5, if the toilet is needed to be drained, the water must overcome the air pressure in the drain tube 4, by extending the flush time to add the water quantity to the urinal 2, thus siphon can be produced between the upper trap 3 and lower trap 5 so as to let the waste in the urinal 2 to be siphoned to the down drain outlet 6, so the water-saving is not very well in this toilet.